Temperature control system



United States Patent Oitce 3,165,149 Patented Jan. 12, 1965 This invention relates to method and apparatus `for conrolling the temperature of a system. In one aspect the invention relates to controlling a temperature bath. In another aspect the invention relates to a chromatographic analysis system adapted to operate at reduced temperatures. In yet another aspect the invention relates to method and apparatus for regulating the temperature in an instrument housing. In a still further aspect the invention relates to method and apparatus for controlling the temperature in a system within the range of ambient temperature. p.

A standard practice for controlling the operating temperature of laboratory and automatic on-stream instruv.ment is to thermostat the instrument at a suiciently high temperature, such as 150 F., so that some supplementary heat must be added by the control system at the highest ambient temperature. Additional amounts of supplemental heat must be added by the control system at lower ambient temperature.

` of said object forfmanipulating Y second three-way valves in heat exchanging relationship with said object,rand means responsive to the temperature said iirstand second threeway valves to control the ratio of hot huid to cold fluid passed in heat exchanging relationship with said object.

Accordingly, it is an object of the invention to provide an improved temperature control system. Another object of the invention is to increase the efciency of operation of various instruments. Yet another object of the invention is to provide for an improved chromatographic analysis system. A still further object of the invention is to provide an improved control system for regulating a temperature within the normal range of ambient temperatures. Another object oi the invention is to providel improved method and apparatus for regulating temperatures within an instrument housing. A still further object of the invention ture control system,

However, many instruments such as the chromatof graphic analyzer, operate at significantly increased eiliciency at lower temperature, such as in the range of 40 F. to 140 F. Complications arise, however, when the desired operating temperature of the instrument is within the normal range of ambient temperature.' One of these complications is that part of the time there is a need for supplemental heat to be added to the system and part of the time there is a need for heat to be removed from the system.

In accordance with the present invention there is provided an improved temperature control system for maintaining the temperature of an object at a substantially constant desired value which can be within the normal range of ambient temperature comprising a Hilsch vortex tube having an inlet, a hot duid outlet conduit and a cold fluid outlet conduit, a source of fluid at ambient temperature, conduit means for passing uid from said source to the inlet of the vortex tube, means for passing the liuid from said cold uid outlet conduit in heat exchanging relationship with said object, valve means positioned in said hot fluid outlet conduit, and means for regulating said valve means responsive to the temperature of said object.

In accordance with a further aspect of the invention there is provided an improved explosion-safe temperature control system for maintaining the temperature of an object at a substantially constant predetermined temperature which can be within the normal range of ambient temperaturc comprising a Hilsch vortex tube having an inlet, a hot iuid outlet conduit and a cold uid outlet conduit, a source of fluid at ambient temperature, conduit means for passing fluid from said source to the inlet of the vortex tube, first and second three-way valves having the inlet thereof connected to said `cold uid outlet conduit and said hot uid outlet conduit, respectively, means for passing uid from the rst outlet of each of said rst and from column ll. A sample conduit Other aspects, objects, and advantages of the invention will be apparent from a study of the disclosure, the drawings, and the appended claim to the invention.

In the drawings FIGURE l is a schematic representation of a control system in accordance with the invention in `combination with a chromatographic analysis system, and FIGURE 2 is a schematic representation of an eX- plosion proof temperature control system in accordance with the invention Referring now to the drawing and to FIGURE 1 in detail there is shown a housing it?, which can be made of thermal insulating material, and which contains a conventional chromatographic column 11 which is lled with a packing material that selectively retardsl passage therethrough of constituents ofa iiuid mixture `to be analyzed. A carrier gas is introduced into the first end of column Il through a conduit 12. A conduit I3 removes the eilluent I4, having a control valve 15 therein, communicates with the first end of columnll. Valve I5 is opened periodically for a preselected time interval by means of a timer 16 so as to introduce a predetermined volume of uid sample to be analyzed into column Il. Although shown schematically, valve l5 can be any type of sample valve known in the art which permits the introduction of a predetermined volume of fluid sample.

First and second sensing elements 17 and i8 are disposed in respective conduits 12 and 13. These elements are adapted to compare a property of the liuid flowing through the two conduits to provide an indication of differences therebetween. These detecting elements are advantageously temperature sensitive resistance elements. The detecting elements are connected into a measuring circuit 19 which can be any suitable measuring circuit known in the art.

Before the sample fluid is introduced into column l1, carrier gas iiows through conduits 12 and 13 so that elements 17 and 18 respond to the same liuid and have identical outputs. Valve l5 isv then opened to introduce a sample into column 11. The carrier gas elutes the constituents of the sample from the column in `sequence so that element 18 responds sequentially to these individual constituents.

In order to maintain the temperature in housing 10 at a substantially constant value within the normal range of ambient temperature, gas from a suitable source at arnis to provide an explosion proof tempera-V by a temperature sensor-transmitter 2S to maintain such temperature substantially constant at a predetermined desired temperature. ln an alternative embodiment, heater controller 24 can provide a constant flow of current through heating element Z3.' Heating the gas and then cooling it to the desired temperature is advantageous in avoiding the condensation of material, for example Water vapor, which might occur ii the gas was iirst cooled and then heated tothe desired temperature.

lilsch vortex tube 22 is also provided with a hot iiuid outlet conduit 2o and a cold fluid outlet conduit 2"?. The operation of a Hilsch vortex tube is based on the Rangue- Hilsch effect. The gas passing through the inlet opening enters a tangential entry nozzle producing a vortex in the internal chamber. Energy distribution at this point issuch that the heated fraction of the gas passes through the hot exit of tube 22, and conduit 26, while the cooled fraction of the gas, selected Afrom the'center mass of the vortex-by a restricting oriiice emerges through conduit 27. A more complete descripticmv of the vortex tube is set forth in U.S. Patent 1,952,281, issued March 27, i934, and which is incorporated herein by reference. The drop in temperature belovv'that of the inlet gas increases as the pressuredrop between the inlet and cold outlet increases. Porl a given inlet pressure and outlet pressure, the temperature drop will be substantially constant regardless ot variations in the inlet gas temperature.

The cooled'gas from conduit 27v passes through Venturi Section 28 to cause intimate mixirn7 of the gas with the gas already in housing lli. The mixed gas passes through conduit 29 and into housing 10. A temperature sensing ymeans 3i, such as a thermocouple, transmits a signal to temperature controller 32 representative'of the temperature Within housing itl. In accordance with the invention a valve 33 is operatively positioned in conduit 26 andl is manipulated by the output of temperature controller 32. vThe thermal response time of the vortex tube is substantially less than that of conventional indirect fluid heat exchangers or radiant heaters, and thus the regulation of the back pressure on the hot uid outlet conduit provides a faster responsetime than, for example, varying the temperature of the inlet air by means of varying the current through an electrical radiant heater. in accordance with the presently preferred embodiment of the invention, temperature controller 32 is a proportional time controller which oscillates valve 33 between its opened and closed positions With the ratio of the period of time each cycle that valve 33 is closed to the period of time each cycle that valve 33 is opened being varied responsive to the output of temperature sensortransmitter 31. The frequency of oscillation is preferably chosen sutlicientlyhigh to substantially avoid effecting a corresponding oscillation in the temperature of the object being regulated. The time required to change between cooling and non-cooling phases is almost instantaneous, thus eliminating diiiculties encountered in time lag of heaters or indirect lluid coolers normally used to control a temperature.

While the yproportional time controller is the presently preferred embodiment, controller 32 can be any suitable control means, for example, an on-off controller or a proportional band controller. In the ori-off control system a drop irl-temperature of the obiect being regulated belovv the desired temperature would cause controller 32 to close valve 33, and thus cease the cooling operation of the vortex tube, until the temperature had risen to a value above the desired temperature, at Which time controller 32 would open valve 33, and thus resume the cooling operation, until such time as the temperature again dropped below the desired value. In the proportional band control system valve 33 acts as a variable restriction and the temperature of the object is raised or lowered by decreasing or increasing, respectively, the iiovv through conduit 26. The proportional time control is presently preferred because of its rapidity and accuracy of response` Valve 3d in conduit T25 can be utilized to remove excess rluidrom housing lil.

l now to FGURE 2 there is shown a modification ot FiGUiE l wherein hot huid outlet conduit 26 and cold rluid outlet conduit 27 are connected to the inlet ports of three-way valves 3e and 37, respectively. First outlet ports or" valves Se and 37, can be connected to a suitable vent by Way of conduits 3d and 39, respectively. rifhe second outlet ports of valves 3d and 37 are connected by way of conduits di and l2 to conduit e3 .ch feeds Venturi section Ztl. Temperature controller 32 regulates valve 36 to vary the amount of hot Fluid from conduit 26 which is passed into conduit d3 by venting the remainder. Similarly temperature controller 32 regulates valve 3'? to vary the amount o cold iiuid passed from conduit E? to conduit 43 by venting the remainder. Thus controller 3,?- controls the ratio of the amount of hot iuid to the amount of cold fluid introduced into conduit 133, and thereby controls the temperature of the combined fluid.

The embodiments of liGURES l and 2 are particularly advantageous where it is desired to provide an explooien-safe system in that the use of electrical heating elements can be avoided While maintaining an accurate control system with fast response.

TWhile ti e heat exchanging iluid presently preferred for utilization in the vortex tube is air, any suitable fluid can be utilized. lWhile the invention has been illustrated in combination with a chromatographic analysis system, it is Within the contemplation of the invention to control the temperature in any instrument housing, temperature bath, or the temperature of any object, for example, refractometers, capacitance measuring devices, gravitometers, and the like. While the invention has been illustrated for controlling a temperature Within the normal range of ambient temperature, it can be utilized to heat above or cool below such range. Thus, it is Within the contemplation of the invention to reverse the position of the vortex tube in FIGUR l such that conduit Z7 is the hot liuid outlet conduit and conduit 26 is the cold iluid outlet conduit.

Reasonable variation and modification are possible within the contemplation of the foregoing disclosure, drawing and appended claim to the invention.

We claim:

A temperature control system including a chromatographic analyzer and means for maintaining the temperature of said chromatographic analyzer at a substantially constant value within the normal range of ambient temperature which comprises a vortex tube having an inlet, a hot fluid outlet and a cold fluid outlet; a source of fluid at ambient temperature; conduit means for passing uid trom said source to said inlet of said vortex tube; heating means in heat transferring relationship with the fluid in said conduit means for heating the fluid in said conduit means to a predetermined temperature above maximum ambient temperature; means for passing only fluid from said cold uid outlet in heat exchanging relationship with said chromatographic analyzer; a hot huid outlet conduit connected to said hot fluid outlet; an on-oi valve means positioned in said hot iluid conduit to completely close said hot duid outlet when said valve means is in its off position; means for measuring the temperature of said chromatographic analyzer and establishing a first signal representative thereof; a proportional time temperature controller; means for applying said first signal to an input 5 5 of said proportional time temperature contioller, and 1 effecting a corresponding oscillation in the temperature of means responsive to the output of said proportional time said chromatographic analyzer. temperature controller for actuating said valve means between the on position to cause said vortex tube to eeet References Cmd 1n the me of thls Patent a temperature drop in the uid between said inlet and 5 UNITED STATES PATENTS said cold fluid outlet and the of position to prevent said 2,533,906 van Guilder Jan 29, 1952 vortex tube from effecting a temperature drop in the uid 2,737,928 Machlanski Mal.. 6, 1956 between said inlet and said cold iiuid outlet, the fre- 2,819,590- Green jam 14, 195g quency of oscillation between said on position and said 3,062,037 Dgymer et a1 NOV 6, 1962 o position being suciently high to substantially avoid 10 3,122,014 Dobbins Feb. 25, 1964 

